New York, New York - Taylor Swift has treated fans to four new songs, and one of them – Patient Zero – has sent Swifties into sleuth mode as they try to uncover the track's toxic inspiration.

The 36-year-old's newest single, which dropped as part of The Life of a Showgirl: The Encore on Friday, sees Taylor reflect on a toxic romance now that her ex has found a new flame.

"But if you wanna party with somebody who might know / About the devil on his shoulder under his halo," she sings.

"When the toxins take their hold, you'd rather die than let it go / But if you're sick of him, I got you, I was patient zero."

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At first, the ill-fated relationship described in the song reminded many of her brief fling with Matty Healy, which also appeared to inspire her 11th album, The Tortured Poets Department.

It certainly lines up: The 1975 frontman soon began dating his now-wife, Gabbriette Bechtel, after his split from Taylor, so this could be the Karma singer reflecting on that.

But there's a big catch. The Tortured Poets Department songs widely believed to have been inspired by the demise of her relationship with Matty indicate that he broke up with – or even ghosted – Taylor.

In Patient Zero, she instead describes herself as "someone who had him and walked away."

This led Swifties to explore a different rabbit hole: Could Patient Zero actually be inspired by Joe Alwyn?

Taylor dated the 35-year-old actor for six years before their surprising split in 2023. According to insider reports, the Opalite artist was the one who initiated the split.

Along with this, Swifties have pointed to some similarities between Patient Zero and other tracks presumably written about Joe.

Her heart-wrenching breakup ballad You're Losing Me hears her sing, "I can't find a pulse, my heart won't start anymore," while in the new song she says, "When the toxins take their hold / You’d rather die than let it go."

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However, some fans aren't convinced, and instead they're pointing to a different Joe who may be the inspo: Joe Jonas!

This theory just might be the most convincing, as it lines up with what Taylor herself has said about the song.

Speaking with CapitalFM, Taylor explained that Patient Zero was inspired by a conversation with friends, where one revealed she'd been reached out to by an ex's new girlfriend who was asking for "guidance."

"Everyone in our group just immediately started saying, like, 'Oh, I've been through that too', and telling the stories of when this kind of reach-out had happened for them," she said.

Back to Joe Jonas: Taylor briefly dated the Jonas Brothers star all the way back in 2008. In 2023, Joe and his then-wife Sophie Turner announced they were getting a divorce.

Soon after, Sophie was spotted at dinner with Taylor, and insiders soon revealed that the singer was letting Sophie stay in her New York apartment as divorce and custody negotiations played out.

"so my patient zero theory is that she wrote this song for Sophie Turner amidst her very public divorce with Joe Jonas. Joe & Taylor were each other's first public romances, making her 'patient zero,'" one fan said on X. "She heard the rumors about their breakup, & wasn't surprised when sophie called."

While this mystery hasn't been solved just yet, there's one new track fans don't need to wonder about: On Cleveland!, Taylor sings for the first time about her wedding to Travis Kelce.

"He already took me to Cleveland / Now I'm wearing white, so hate all you like."